The present invention relates to a drill chuck. More particularly this invention concerns such a chuck which can be locked so that it does not loosen during use.
A standard drill chuck has a body centered on and rotatable about an axis and formed with a plurality of angled guides opening axially forward at a front chuck end and respective jaws axially and radially displaceable in the guides and each formed with a row of teeth. A metallic tightening ring axially fixed but rotatable about the axis on the body has a screwthread meshing with the teeth so that rotation of the tightening ring displaces the jaws in their guides. An adjustment sleeve is rotatable about the axis on the body on a metallic intermediate ring fixed on the tightening ring and is coupled to the tightening ring to rotate it and set the position of the jaws of the chuck.
In the system described in U.S. Pat. No. 5,829,761 the adjustment sleeve rotatable about the axis on the body has a hard outer part and an inner part of a softer material fixed on the outer part. The metallic intermediate ring fixed on the tightening ring has formations coupled to the hard outer part and the inner part rides on the intermediate ring.
The hard, normally steel, outer sleeve part is resistant to damage during normal use so that if a wrench must be applied to it, for instance, it will not be ruined. Since the intermediate ring is coupled directly to this hard outer ring, no torque is transmitted by plastic parts and, therefore, the adjustment ring can be actuated forcibly without damage to it. On the other hand the inner part is made of plastic which can easily be formed, for instance by molding, to have a very complex shape and which can be counted on to ride smoothly on the metal intermediate ring. Such a chuck is much cheaper to manufacture than one with a one-piece tightening ring where normally the complex internal surface must be formed by an expensive and slow machining operation.
It is therefore an object of the present invention to provide an improved lockable drill chuck.
Another object is the provision of such an improved lockable drill chuck which overcomes the above-given disadvantages, that is which is inexpensive to manufacture yet whose adjustment sleeve is of one-piece metallic construction.
A further object is to provide an economical method of making the critical outer sleeve of the chuck.
A lockable drill chuck has according to the invention a body centered on and rotatable about an axis and formed with a plurality of angled guides opening axially forward at a front chuck end, respective jaws axially and radially displaceable in the guides and each formed with a row of teeth, and a tightening ring axially fixed but rotatable about the axis on the body and having a screwthread meshing with the teeth so that rotation of the tightening ring on the body in a tightening direction displaces the jaws in their guides toward one other and rotation in a loosening direction displaces the jaws away from one other. A one-piece outer sleeve rotatable about the axis on the body is formed unitarily with a pressed-in radially inwardly projecting cam formation. A locking member is displaceable by the cam formation between a locked position braced between the chuck body and the tightening ring for blocking rotation about the axis of the tightening ring on the body in the loosening direction and an unlocked position for permitting such rotation. The outer sleeve is metallic, of substantially uniform wall thickness, and formed with an outwardly open pocket at the cam formation.
Thus the instant invention uses a sleeve which can be produced at low cost with no material-removing machining. The sleeve is made by a simple pressing operation. To this end in accordance with the invention a die is pressed against an outer surface of the sleeve over the recess to form an inwardly projecting cam formation on the sleeve. More particularly a mandrel is fitted inside before pressing the die against the sleeve. This mandrel is radially expanded into tight engagement with an inner surface of the sleeve before pressing the die against the sleeve, and radially contracted out of contact with the inner sleeve surface after pressing the die against the sleeve. In a similar manner, a clip-receiving groove is formed in the sleeve by pressing a tool into radial engagement with the sleeve all around the sleeve. All of these operations are carried out purely by deforming the axially symmetrical workpiece, that is without any complex and difficult machining operations. Thus the sleeve is produced at very low cost.
According to the invention the outer sleeve is formed with a plurality of such cam formations and respective pockets spaced angularly about the axis. In addition a shield cap can be fixed to the chuck body at the front end thereof to cover a front end of the outer sleeve.
The locking system includes an array or radially outwardly directed teeth formed on the chuck body. The locking member includes a tooth part engageable with the teeth, a spring part urging the tooth part out of engagement with the teeth, and a cam part engageable with the cam formation and displaceable radially thereby jointly with the tooth part. The teeth are sawteeth having steep flanks directed in the loosening direction.
The drill chuck further has according to the invention an inner sleeve fixed rotationally to the locking ring coaxially within the outer sleeve and having an end juxtaposed with an end of the outer sleeve and formations on the sleeve ends for forming a lost-motion rotational coupling between the sleeves so that the outer sleeve can move limitedly angularly relative to the inner sleeve between one end position with the cam formation engaging the cam part and pressing the tooth against the teeth and an opposite end position with the cam formation out of engagement with the cam part. A spring releasably retains the outer sleeve in its end positions. This spring prevents the chuck from moving into the unlocked position during drilling, and holds the parts in the unlocked position during loosening.
The formations on the sleeve ends include at least one axially directed finger of predetermined angular dimension formed on one of the sleeves and a cutout formed in the other of the sleeves, receiving the finger, and of a substantially greater angular dimension than the finger. The outer sleeve is formed at the front end with a plurality of such fingers angularly spaced about the axis. The inner sleeve is formed with a plurality of such cutouts receiving the fingers. The outer sleeve is unitarily formed with the fingers which can extend axially back from a front end of the outer sleeve. In this case the fingers extend at an acute angle to the axis.
The locking member according to the invention can have two such tooth parts and two such respective cam parts. The outer sleeve has two such cam formations engageable with the locking-member cam parts. Alternately the locking member can have opposite ends forming the tooth parts and be formed therebetween with the spring part and cam parts. In another system the chuck has two such locking members angularly offset from each other and the sleeve has two such cam formations engageable with the respective cam parts.
The locking member is normally formed according to the invention of a single elastically deformable metallic strip, typically of spring steel. It can be formed with undulations so that it has a damping effect.
A snap ring is set in the front end of the chuck and bears axially backward on the sleeve. In addition the outer sleeve is formed with a plurality of angularly spaced slots and an annular spring clip is engaged around the outer sleeve and has parts projecting through the slots and bearing axially forward on the chuck body. In another system a washer is engaged between a rear end of the chuck body and a rear end of the outer sleeve. This washer can be fixed to the chuck body and axially coupled to the outer sleeve. In this case the outer sleeve has at its rear end an inwardly open groove receiving an outer edge of the washer. Such a washer has a plurality of radially elastically deflectable arms having radially outer ends forming the washer outer edge and received in the groove of the sleeve.